There’s a more comprehensive guide from the Assembly Research Service (pdf).

In short, the law intends to preserve/enshrine EU law in devolved policy areas within Welsh law after Brexit.

At the moment, the UK Government are attempting to do this via their own Brexit Bill. However, there’s negotiations between the Welsh, Scottish and UK Governments over what EU powers, regulations and laws will be devolved after Brexit (full list here – pdf) have so far failed. Due to this, the Welsh Government decided to preserve the status quo as much as they can to prevent the UK Government making laws in (otherwise) devolved areas without the permission of the Senedd.

In January 2018, AMs unanimously backed a proposal by Steffan Lewis AM (Plaid, South Wales East) to introduce such a “Continuity Bill”. The timetable for the introduction of the law accelerated after a failure in the latest round of negotiations between the governments; two weeks ago the Welsh Government announced they would introduce the Bill and last week AMs voted (as below) in favour of it being treated as an emergency law:

For clarification, Gareth Bennett AM (UKIP, South Wales East) voted against. The Tories presumably did because this action directly opposes the UK Government.

Why is it being treated as an emergency law?

From April 1st 2018, Wales will have a reserved powers model. The UK Government’s Brexit Bill (as it’s currently drafted) contains clauses to prevent Wales from modifying EU laws as they relate to devolved areas and restricts the power of Welsh Government Ministers when making regulations relating to retained EU laws after Brexit.

If the Continuity Bill is passed before April 1st – the timetable is currently set for March 21st 2018 (yes, next Wednesday) – then this should, in theory, prevent such a “power grab” and would maintain the status quo when it comes to the devolution settlement.

As for the disadvantages of it being an emergency law, there’ll be no public consultation, no committee processes or reports (the Assembly as a whole will do this, starting this afternoon) and no detailed analysis of the costs – all of which could affect scrutiny of the Bill.

The Lowdown: 3 Key Proposals in the Continuity Bill

1. It enshrines existing EU laws in Welsh law (in devolved areas)

This is the main aim of the Bill. It’ll grant Welsh Government ministers the power to make amendments to EU laws with regard Wales so they can still function after Brexit (i.e. changing names, replacing references to EU institutions with Welsh or UK institutions). It’s hoped this would provide certainty to citizens and businesses.

The UK Government will also have to ask Wales’ permission before changing anything relating to EU law in devolved areas after Brexit.

2. You won’t be able to challenge the validity of retained EU laws after Brexit

This basically means the validity of any EU laws enshrined in Welsh law after Brexit will be interpreted based on case law at the European Court of Justice (ECJ) – with a few exceptions, such as the ECJ ruling that a law/regulation is invalid.

3. Wales could maintain the same regulations as the EU after Brexit

Section 11 of the Bill will grant Welsh Government Ministers the power to make regulations in devolved areas so Wales can align with and keep pace with EU law after Brexit. For example, the Welsh Government could ensure Welsh goods comply with EU laws even if the UK is outside the single market – which might help trade and exports.

How much will the Continuity Bill cost?

That’s unclear. Apart from the cost of drafting and passing the Bill and its associated regulations themselves, the Welsh Government admit they don’t know.

They say in the explanatory memorandum that such is the uncertainty they didn’t want to put any figures out in case those figures were misleading.